Sertoli-Leydig cell tumors of the ovary are rare diseases that occur primarily in young women. The majority of these tumors are unilaterally localized, and conservative surgery is sufficient. However, these tumors exhibit a variety of histological patterns, which are significant prognostic factors. To date, no standard therapy exists. Here we report 4 cases of Sertoli-Leydig cell tumors of the ovary. One patient whose tumor was a poorly differentiated Sertoli-Leydig cell tumor with mesenchymal heterologous elements received adjuvant chemotherapy postoperatively but died of disease 2.5 years after surgery. The other 3 patients remained free of disease during follow-up. Conservative surgery is an appropriate treatment for young patients with Sertoli-Leydig cell tumors. Those who have poor prognostic factors may need adjuvant chemotherapy with a combination of bleomycin, etoposide and cisplatin.